I like how the article adds weight to mainstream vs fringe. But it occurs to me that some ideas are given so little attention that there is no substantial basis of what is fringe and what is mainstream.
(Long time since I _attempted_ to create an article on Wikipedia, but the form of entries makes it clear) factual assertions must largely be supported by (some metric) of published sources. A fringe topic would by definition would have “so little attention”. So it stands to reason Wikipedia would need a _policy_ of supporting fringe in order to allow page creation.
In other words, fringe is what has few supporting references, but is otherwise noteworthy. With a number of notable exceptions.
If an idea is given a lot of attention, it might be mainstream or fringe, depending on how accepted it is. It might be getting a lot of negative attention, or it might just be getting a lot of attention right now. It might be transitioning from fringe to mainstream.
But if it is not getting any attention, or very little, then it is by definition fringe.